Rotary armature flux shifting device



Jan. 31, 1967 Filed March 2, 1965 s. E. zocHoLL. 3,302,146

ROTARY ARMATURE FLUX SHIFTING DEVICE 2 Sheets-Sheet 1 Jfin,v 3l, 1967 s,E ZQCHOLL 3,302,146

ROTARY ARMATURE FLUX SHIFTING DEVICE Filed March 2, 1965 2 sheets-sheeta www-e www 3,302,146 ROTARY ARMATURE FLUX SHIFTING DEVICE Stanley E.Zocholl, Philadelphia, Pa., assignor to I-T-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 2, 1965,Ser. No. 436,578 2 Claims. (Cl. 335-230) This invention relates to amagnetic trip device for current interrupters, and more specificallyrelates to a magnetic trip device having a rotary armature.

Magnetic trip devices for circuit interrupters are well lknown to thoseskilled in the art, and are illustrated typically in copendingapplication Serial No. 248,463, iled January 4, 1963, entitled StaticOvercurrent Relay, and assigned to the assignee of the instantinvention. Generally, these devices include a magnetic body having anarmature which can be sealed thereto with the armature ultimatelycontrolling the motion of a pair of cooperating contacts whereby, whenthe armature is released from its magnet, this motion can permit orcause the contacts to be moved to their open position, while when thearmature -is sealed to its magnet, the contacts of the interrupter areretained in their engaged position.

In the prior art type devices, the magnet which seals the armaturecommonly is provided with two parallel magnetic paths which each includethe movable armature. The rst path is a relatively low reluctance pathwhich has a suitable source of magnetic llux therein such as a permanentmagnet. The other path, which is a relatively high reluctance path, thenhas a control winding therein which normally generates magnetic flux insuch a direction as to decrease the ilux passing to the armature. If nowthe current in this control winding is increased, the net flux throughthe armature will be further decreasedy to a point below the valuerequired to seal the armature to the magnet body.

This type of arrangement is highly desirable since the ampere turnsgenerated by the control coil are not required to generate the holdingflux, but merely control the holding iluX from some other source. Thus,a relatively small number of ampere turns can release the armature.'I'his llux shifting technique, however, has one serious disadvantage inthat, as the control coil current is increased to buck down the flux inthe armature path from permanent magnet or other suitable source, it ispossible that the coil current can increase to a point where thearmature flux passes through zero and thereafter increases in theopposite polarity. As this reversed flux increases, the holding forcefor the armature increases so that the armature can be pulled closed ifit has not attained a large enough air gap during the period when theholding force was less than the opening force applied to'the armature.

This pull-in problem becomes especially troublesome in environmentswhere the latching mechanism is subject to mechanical shock, since theunbalanced armature which moves in a linear direction can be caused,through shock, to be moved toward the magnet body where it can besubject to this pull-in force.

The principle of the present invention is to provide a novel magnetstructure using the concept of ux shifting described above where,however, the armature is a rotatable body which is dynamically balancedabout its axis of rotation. Thus, mechanical shock forces will not causethe armature to move back toward the magnet pole faces, therebydecreasing the possibility of its being trapped by the pull-in force ofthe magnet due to the rapid increase of control current in the controlWinding.

As a further feature of the invention, the novel rotary armature isdesigned to have two pairs of poles at the A United States Patent O ICCrespective opposite corners of the rotary mem-ber wherein a rstdiagonally arranged pair are normally sealed to the magnet structure,while, when the armature rotates, the second diagonal pair engage themagnet structure faces, thereby retaining the armature in its engagedposition in the event that control current builds up to a sufficientlyhigh value which would otherwise return the main diagonal pole faces totheir sealed-in position.

Accordingly, a primary object of this invention is to provide a novelmagnetic latch structure for circuit interrupters.

Another object of this invention is to provide a magnetic latchstructure which has a rotatable armature.

A further object of this invention is to provide a novel armature for amagnetic latch structure which pivotally rotates about its center ofinertia.

Another object of this invention is to provide a novel magnetic latchstructure which is not subject to pull-in forces subsequent -to releaseof the armature.

Still another object of this invention is to provide a novel rotaryarmature for a magnetic latch structure which is magnetically sealed inthe armature open position as well as in the armature closed position.

These and other objects of this invention will become apparent from thefollowing description when taken in connection with the drawings, inwhich:

FIGURE 1 schematically illustrates a typical prior art magnetic latchstructure.

FIGURE 2 is a diagram of the magnetic holding force on the armature as afunction of the ampere turns generated by the control winding -in FIGURE1.

FIGURE 3 is a side plan view of the novel latch structure of theinvention.

FIGURE 4 is a side View of FIGURE 3 with the rotating armature -in itssealed position.

FIGURE 5 is similar to FIGURE 4, and illustrates the armature of FIGURE4 in itsopen position.

FIGURE 6 is a side plan view of a second embodiment of the invention.

FIGURE 7 is a side view of FIGURE 6 with the armature in its closedarmature sealed position.

FIGURE 8 is similar to FIGURE 7, but illustrates the armature rotated toits sealed open position.

Referring rst to FIGURE l, I have schematically illustrated therein atypical prior art magnetic latch system using the flux shiftingtechnique. Thus, in FIGURE 1, a magnetic structure is provided which hastwo yokes 10 and 11 connected by magnet legs 12, 13 and 14. The leg 12has a permanent magnet 15 inserted therein, or some other suitablesource of unidirectional flux such as a D.C. winding.

The leg 13 then has an air gap 16 therein, and carries the controlwinding 17 which can be connected to positive and negative D.C.terminals 18 and 19, which are connected to some suitable source and arein series with a circuit control means such as variable resistor 20.

The leg 14 has an air gap 22 therein for defining a flux path through amagnetic armature 23. Magnetic armature 23 is then connected to asuitable shaft 24 which is connected to a biasing spring 25, which isxed at its upper end as illustrated, and pulls armature 23 away from themagnet structure with some predetermined spring force.

The armature 23 or its extending shaft 24 is then suitably connected, asillustrated by dotted line 26, to a movable contact 27 which moves intoand out of engagement with stationary contact 28. That is to say, whenarmature 23 is sealed in the position illustrated in FIGURE l, contacts27 and 28 are closed. When, however, the Varmature 23 is moved away fromits sealing lposition by spring 25, contacts 27 and 23 are open. Notethat the armature 23 could either operate the contacts directly or,alternatively, could operate a latch mechanism which, in turn, controlsthe contact position of contact 27.

In operation, the permanent magnet 15 generates a flux having componentsp1 and 152. The flux component p2 is substantially higher than p1 inview of the air gap 16 Vin leg 13. The control Winding 17 then generatesa ux having the components Q53 and p4 shown in FIGURE l, where thecomponent p3 is in opposition to the ux p2, while the component o4 isadditive with component 451.

So long as flux component o2 is suciently greater than 953, the net fluxthrough armature 23 will be sufficient to hold it sealed to the magnetbody. When, however, it is desired to release armature 23, and thus opencontacts 27 and 28, the current through coil 17 is increased as byappropriate adjustment of `adjustable resistor 21) so that the net fluxq523 decreases to a suiciently low value to permit spring 25 to move thearmature out of its sealed engagement with its magnet body.Alternatively, the connection lof an additional D.-C. voltage signal toterminals 1S. and 19 through some automatic sensing circuit, or thelike, could cause the required current increase in coil 17 to decreasethe net armature linx.

FIGURE 2 shows the holding force FH as a function ofv the` armature fluxtpg-Q53. The curve of armature flux q523 is a straight line whichcrosses zero flux and goes negative as N11 increases. FH is obtained bysquaring this aramture flux q52-q53, which results in the parabolashown.

A major difculty with this type arrangement is schematically illustratedin FIGURE 2 wherein it is seen that the holding force holding thearmature 23 against the magnet will decrease below the spring force toobtain release of armature 23 with a suitable increase of the ampereturns N11, where, however, a continued increase in the ampere turns Nilwill again cause the holding force to increase above the spring force ofspring 25.

Under this condition, and if the armature 23 has not moved far enoughaway from the magnet at the time the holding force is increased beyondthe spring force, the armature will inadvertently be pulled in. Thiscondition is aggravated in the presence of mechanical shock forces whichcould tend to cause the anmature 23 to be jarred toward the pole facesof the magnet, thus increasing the likelihood of recapture by the magnetafter` the control current is increased by a suflicient value.

In accordance with the present invention, a novel structure is providedwherein the armature 23 is caused to be a rotary armature which rotatesaround its center of inertia, whereupon mechanical shock forces aredynami- `cally balanced and will not tend to move the armature backtoward the magnet.

A rst embodiment of the invention is illustrated in FIGURES 3, 4 and 5,wherein the magnet is formed of two magnetic yokes 311 and 31. Theright-hand end of yokes 31) and 31 are then connected together through apermanent magnet 32 which has ya North pole on its upper face and aSouth pole on its lower face. The connection between yokes 311 and 31and permanent magnet 32 are effected by suitable bolts such as the bolt33 in FIGURE 3 which is captured by nut 34.

A second leg connecting yokes 30 and 31 is the leg 35 which receives thecontrol coil 36 which has extending leads 37 and 38. The leg 35 issecured to the upper yoke 31 by suitable screws such as screw 35a wichextends into suitable tapped openings in leg 35. The leg 35 has a lengthless than the spacing between yokes 30 and 31 so that an air gap 35h isdefined between leg 35 and yoke 30. Coil 36 is equivalent to coil 27 ofFIGURE l.

The left-hand end of yokes 30 and 31 are then joined by a nonmagneticbearing block 39 which could be of brass and has a central openingtherein. The bearing block 39 is secured between yokes 311 and 31 as bysuitable screws 39a, 39h, 39C, 39d and 39e. This central openingrotatably receives a shaft 4t) extending from the rotatable armature 41.The shaft 4t) may then be operatively connected to a latching mechanismor may be connected directly to the movable contact 50 which cooperatesWith stationary contact 51, as schematically illustrated in FIGURE 3.

As further schematically illustrated in FIGURE 4, the armature 41 isoperatively connectedl to the biasing spring 52 which biases armature 41for rotation in a clockwise direction, and out of the sealing engagemntshown in FIGURE 4 and toward the position of FIGURE 5. Note that thespring 52 could be connected to shaft 40, if desired.

The operation of the magnet structure of FIGURES 3, 4 and 5 issubstantially identical to that of FIGURE l, where FIGURE 3 indicatesthe flux components 1p1, o2, p3 and o4 in a manner similar to that ofFIGURE 1. Thus, in operation, the leads 37 and 38 of coil 36 haveimpressed thereon a suitable current for generating a flux component Q53in opposition to the flux component p2 whereby a net flux passes through:armature 41 which is su'icient to retain it in the sealed position ofFIGURE 4. When, however, it is desired to open contacts 51) and 51, thecurrent through coil 36 is increased, whereupon flux component q53increases to buck down flux component 9152 until the holding force onthe armature 41 decreases below the spring force of spring 52, whereuponthe Iarmature is rotated to the position of FIGURE 5.

Note that since the armature 41 is dynamically balanced around thecenter of shaft 40, mechanical shocks applied to the device will nottend to move the pole faces of armature 41 toward the corresponding polefaces of yokes 30 and 31, thus decreasing the likelihood of aninadvertent pull-in caused by the continued increase of current in coil36 and the reversal of flux from yokes 31B and 31 through armature 41 toa Value sufficient to pull in armature 41.

In order to further prevent the possibility of pull-in, a secondembodiment of the invention illustrated in FIG- URES 6 through 8provides a second pair of pole faces for the rotating armature whichinsures that the pull-in force will retain the 'armature in its openposition. Thus, referring to FIGURES 6, 7 and 8 wherein componentsidentical to those of FIGURES 3, 4 and 5 are given similiar identifyingnumerals, the shape of the armature has been altered to that shown forthe armature 60.

Thus, in FIGURES 6, 7 and 8, the Iarmature 60 has two pole faces 61 and62 similar to the pole lfaces provided for armature 41 in FIGURES 3, 4and 5, and, in addition has a second pair of diametrically opposed faces63 and 64. Thepole faces 61y and 62 in FIGURES 6, 7 and 8 are thediametrically opposite pole faces which normally seal-in the magnet.

If now the armature 61 is released due to increasing current throughcontroly coil 36 and the spring force of spring 52, and the armature isrotated in al clockwise direction in FIGURES 7 and 8, it willv beobserved that the auxiliary or seal-open pole faces 63 and 64 willapproach the yokes 30 fand 31. If the pull-in force generated by thecontinued increase of coil 36 exceeds the opening force of spring 52,the pole faces 63 and 64 will be adjacent yokes 30 and 31, and it isthese pole faces which will be sealed to yokes 30 andv 31, thusretaining armature 60 rotated in a clockwise direction, as shown inFIGURE' 8, with the excessive and inadvertent pull-in force now aidingthe spring 52 in retaining armature 60 in its counterclockwise position.

Thus, the armature 60, when designed with two diametrically opposedpairs of pole faces, will be accelerated in a clockwise direction andretained in a clockwise direction by a motor action yapplied to armature61);

Although this invention has been described with respect to its preferredembodiments, it is to he understood that many variations andmodifications will now be 0bvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe Specific disclosure herein but only by the claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed lare defined as follows:

1. A magnetic latch structure comprising an armature of magneticmaterial and a magnet strtucture; said magnet structure comprising afirst closed magnetic path including a pair of spaced pole faces and asource of unidirectional miagnetic flux, and a second closed magneticpath including a variable source of ampere turns and said pair of spacedpole faces; said second closed magnetic path having a higher magneticreluctance than said rst closed magnetic circuit; said armaturecomprising a rotatable body of magnetic material having a pair ofditametrically opposite pole faces; pivotal mounting means connected toa central portion of said armature; said arm-ature being disposedbetween said pair of spaced pole faces of said magnet structure; saidpair of diametrically opposite pole faces of said armature engaging-respective pole faces of said spaced pole faces; said armature beingappended rotatable about the said pivotal mounting means to move saidpair of diametrically opposite pole faces away from their saidrespective spa-ced pole faces; and a second pair of diametricallyopposed pole faces on said armature; said second pair of polefaces-being movable into engagement with respective pole faces of saidspaced pole faces when said pair of diametrically opposed pole facesmove away from said spaced pole faces of said magnet.

2. A magnetic latch structure comprising a pair of spaced magnetic yokemembers lhaving iirst and second ends, an end leg magnetic memberextending between said first ends of said pair of spaced magnetic yokemembers, a central leg section extending between central portions ofsaid spaced magnetic yoke members, a nonmagnetic spacer member extendingbetween said second ends 0f said pair of spaced magnetic yoke members,and a rotatable armature pivotally mounted on said non-magnetic spacerand `between magnetic pole surfaces of said sec-ond ends of saidmagnetic yoke members; said end leg magnetic member including iuxgenerating means therein; said central leg section having an air gaptherein; said central leg section having a cont-rol winding woundthereon; said armature having first and second engaging surfacesengaging said respective magnetic pole surfaces of said second ends ofsaid magnetic yoke niembers; said first and second engaging surfacesbeing disposed on opposite sides -of the axis of rotation yof saidarmature; said armature having third land fourth engaging surfacesdisposed on opposite sides of the axis of 'rotation of said armature;said third and fourth engaging surfaces being rotatable into engagementwith said respective magnetic pole surfaces of said second ends of saidmagnetic yoke members when said armature rotates about the axis thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,412,123 12/1946Carpenter. 2,892,055 6/1959 Wantosoh. 3,016,479 1/1962 Coley 317-171BERNARD A. GILHEANY, Primary Examiner. G. HARRIS, Assistant Examiner.

1. A MAGNETIC LATCH STRUCTURE COMPRISING AN ARMATURE OF MAGNETICMATERIAL AND A MAGNET STRUCTURE; SAID MAGNET STRUCTURE COMPRISING AFIRST CLOSED MAGNETIC PATH INCLUDING A PAIR OF SPACED POLE FACES AND ASOURCE OF UNIDIRECTIONAL MAGNETIC FLUX, AND A SECOND CLOSED MAGNETICPATH INCLUDING A VARIABLE SOURCE OF AMPERE TURNS AND SAID PAIR OF SPACEDPOLE FACES; SAID SECOND CLOSED MAGNETIC PATH HAVING A HIGHER MAGNETICRELUCTANCE THAN SAID FIRST CLOSED MAGNETIC CIRCUIT; SAID ARMATURECOMPRISING A ROTATABLE BODY OF MAGNETIC MATERIAL HAVING A PAIR OFDIAMETRICALLY OPPOSITE POLE FACES; PIVOTAL MOUNTING MEANS CONNECTED TO ACENTRAL PORTION OF SAID ARMATURE; SAID ARMATURE BEING DISPOSED BETWEENSAID PAIR OF SPACED POLE FACES OF SAID MAGNET STRUCTURE; SAID PAIR OFDIAMETRICALLY OPPOSITE POLE FACES OF SAID ARMATURE ENGAGING RESPECTIVEPOLE FACES OF SAID SPACED POLE FACES; SAID ARMATURE BEING ROTATABLEABOUT THE SAID PIVOTAL MOUNTING MEANS TO MOVE SAID PAIR OF DIAMETRICALLYOPPOSITE POLE FACES AWAY FROM THEIR SAID RESPECTIVE SPACED POLE FACES;AND A SECOND PAIR OF DIAMETRICALLY OPPOSED POLE FACES ON SAID ARMATURE;SAID SECOND PAIR OF POLE FACES BEING MOVABLE INTO ENGAGEMENT WITHRESPECTIVE POLE FACES OF SAID SPACED POLE FACES WHEN SAID PAIR OFDIAMETRICALLY OPPOSED POLE FACES MOVE AWAY FROM SAID SPACES POLE FACESOF SAID MAGNET.